Temperature Dependency of the Mutagenic Action of N-Methyl-N′-nitro-N-nitrosoguanidine inStreptomyces cacaoi

Abstract

The effectiveness of N-methyl-N′-nitro-N-nitrosoguanidine (NG) in inducing mutations in Streptomyces cacaoi was demonstrated with two systems: reversion to prototrophy of an isoleucine-requiring mutant and the induction of forward mutation of a prototrophic strain. An optimal condition for yielding a high frequency mutation was set as follows: Treatment of spores with 1 mg/ml of NG in 0.016 m phosphate buffer, pH 6, at 42°C for 60 min. In Streptmyces cacaoi, the mutagenesis depended highly on the temperature of NG treatment; elevation of the treatment temperature resulted higher frequency of mutation. Only a little dependency on temperature was shown in Escherichia coli, but the dependency was also observed when the Streptomyces was treated with ethyl methanesulfonate. The significance of these results for considering mechanism of NG action was discussed.